Emissive monomeric metal complexes

ABSTRACT

Monomeric metal complexes having improved luminescence properties are provided. In one embodiment, a monomeric metal complex is represented by the formula [PN]M(L) 2 . PN is an amidophosphine ligand, and M may be any metal capable of exhibiting luminescent properties, for example, a d 10  metal. L may be a tertiary phosphine. Alternatively, a second PN ligand or DPPE may take the place of both L ligands.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to U.S. Provisional Application Ser.No. 60/834,053, filed on Jul. 28, 2007, the entire content of which isincorporated herein by reference.

FIELD OF THE INVENTION

The invention is directed to emissive monomeric metal complexes.

BACKGROUND OF THE INVENTION

Luminescent transition metal complexes have been widely studied fortheir use in biological imaging, photochemical catalysis, andlight-driven fuel production. Conventionally, Pt and Ru based emittershave been used, but the high cost of such emitters has led to theinvestigation of Cu as a lower cost, biologically relevant replacement.To that end, the most thoroughly studied Cu emitters are monomerssupported by modified polypyridine and phenanthroline ligands. However,these complexes suffer from low quantum efficiencies and shortluminescence lifetimes.

In an effort to address the quantum efficiency and luminescence lifetimeshortcomings of the polypyridine and phenanthroline supported Cuemitters, bulky bidentate phosphines using tertiary phosphines andsubstituted phenanthroline ligands in concert have been investigated.These complexes inhibit exciplex quenching, which provides longerlifetimes and improved quantum efficiency. The use of bulky diphosphineligands in simple phosphine complexes of copper halides has also beenresearched. However, although these complexes can be highly emissive inthe solid state in low temperature solvent glasses, they display onlyfaint, short-lived emission in solution at ambient temperatures.

Recently, amide-bridged dicopper complexes, such as [(PNP)Cu]₂(PNP⁻=bis(2-(diisopropylphosphino)phenyl)amide) have been researched.These dimeric copper complexes possess both long lifetimes and highlyefficient emission. However, the complex ligands required to producesuch dimers are difficult to manipulate, which makes changing theproperties of the dimer challenging.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, a monomeric metal complex isrepresented by Formula 1.

As shown in Formula 1, M is bonded to an amidophosphine (PN) ligand andtwo additional ligands (L₁ and L₂). M may be any metal capable ofproducing emission characteristics, for example, M may be a d¹⁰ metal.The PN ligand is represented by Formula 2.

In both Formulae 1 and 2, R₁ and R₂ may each independently be anyhydrocarbon substituent. Also, each of R₃ through R₁₁ can be hydrogen orany other substituent suitable for substituting phenyl rings. The L₁ andL₂ ligands may each independently be a substituent represented by PX₃,where each X group may be any hydrocarbon substituent.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

The above and other features and advantages of the present inventionwill be better understood by reference to the following detaileddescription when considered in conjunction with the accompanyingdrawings in which:

FIG. 1 is a Stem-Volmer plot of k_(obs) vs. concentration of DCQindicating the oxidative quenching of the compound prepared according toExample 2 with 2,6-dibenzoquinone (Q);

FIG. 2 is the molecular structure of the complex prepared according toExample 2 with hydrogen atoms omitted for clarity;

FIG. 3A is the molecular structure of the complex prepared according toExample 3 with hydrogen atoms omitted for clarity;

FIG. 3B is the molecular structure of the complex prepared according toExample 9 with hydrogen atoms omitted for clarity;

FIG. 3C is a depiction of the highest occupied molecular orbital (HOMO)of the complex prepared according to Example 3 as determined by discreteFourier transform (DFT);

FIG. 3D is a depiction of the lowest unoccupied molecular orbital (LUMO)of the complex prepared according to Example 3 as determined by DFT;

FIG. 4 is a cyclic voltammogram of the complex prepared according toExample 2;

FIG. 5A depicts emission/excitation spectra of the complex preparedaccording to Example 2 (λ_(ex)=430 nm);

FIG. 5B depicts emission/excitation spectra of the complex preparedaccording to Example 3 (λ_(ex)=430 nm);

FIG. 5C depicts emission/excitation spectra of the complex preparedaccording to Example 4 (λ_(ex)=430 nm);

FIG. 5 is an overlay of absorption spectra of the complexes preparedaccording to Examples 2, 3 and 4;

FIG. 6 depicts luminescence decay traces of the complexes preparedaccording to Examples 7 (green), 2 (red) and 8 (blue), and an excitationspectrum of the complex prepared according to Example 2 (inset) andnormalized emission spectra;

FIG. 7A depicts emission/excitation spectra of the complexes preparedaccording to Example 7 (λ=430 nm);

FIG. 7B depicts emission/excitation spectra of the complexes preparedaccording to Example 8 (λ_(ex)=430 nm);

FIG. 7 is an overlay of absorption spectra of the complexes preparedaccording to Examples 2, 7 and 8;

FIG. 8 depicts emission spectra of a polycrystalline complex preparedaccording to Example 8 (λ_(ex)=430 nm) at 77 K (black) and 298K (red);

FIG. 9 is an overlay of absorption spectra of the complexes preparedaccording to Examples 2, 9 and 10;

FIG. 10 depicts emission/excitation spectra of the complex preparedaccording to Example 9 (λ_(ex)=430 nm);

FIG. 11 depicts emission/excitation spectra of the complex preparedaccording to Example 10 (λ_(ex)=350 nm); and

FIG. 12 is an overlay of optical spectra of the complex preparedaccording to Example 2 in benzene, diethyl ether, and THF.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to monomeric metal complexes havingexcellent emission and luminescence properties, including long lifetimesand good quantum efficiency. In addition to excellent luminescenceproperties, the inventive monomeric metal complexes are morecost-effective than previously investigated luminescent compounds, andhave structures that are easily manipulable. Ease of manipulation is oneimportant benefit of the inventive complexes because manipulation of thecomplex structure enables easy modification of the properties of thecomplex and easy tuning of the color and luminescence properties of thecomplex.

In one embodiment, a monomeric metal complex is selected from compoundsrepresented by Formula 1.

As shown in Formula 1, M is bonded to an amidophosphine (PN) ligand andtwo additional ligands (L₁ and L₂). M may be any metal capable ofproducing emission characteristics. In one embodiment, for example, M isa d¹⁰ metal. Nonlimiting examples of suitable metals for M include Cu,Ag and Zn. In one embodiment, for example, M is Cu, and these Cucomplexes exhibit unusually long lifetimes (about 16 to about 150 μs),extremely high quantum efficiency (Φ ranging from 0.16 to about 0.70),and variable emission maxima ranging from about 500 to about 550 nm inbenzene at 298K.

The PN ligand may be represented by Formula 2.

In both Formulae 1 and 2, R₁ and R₂ can each independently be anyhydrocarbon substituent, and the hydrocarbon substituents may be eithersubstituted or unsubstituted. Nonlimiting examples of suitablehydrocarbon substituents include substituted and unsubstituted alkylgroups, substituted and unsubstituted alkenyl groups, substituted andunsubstituted alkynyl groups, substituted and unsubstituted aryl groups,substituted and unsubstituted heteroaryl groups, and the like. In oneembodiment for example, each of R₁ and R₂ is an isopropyl group. Inanother embodiment, each of R₁ and R₂ is a phenyl group.

Each of R₃ through R₁₁ can be hydrogen or any other substituent.Substituents for substituting phenyl rings are well known, and any suchknown substituents may be used for R₃ through R₁₁. Nonlimiting examplesof suitable substituents for R₃ through R₁₁ include hydrogen, halogens,hydroxyl groups, cyano groups, alkoxy groups, acyl groups, substitutedor unsubstituted alkyl groups, substituted or unsubstituted alkenylgroups, substituted or unsubstituted alkynyl groups, substituted orunsubstituted aryl groups, substituted or unsubstituted heteroarylgroups, and the like. In one embodiment, at least one of R₃ through R₁₁,for example R₅, is selected from methyl groups and trihalo-substitutedmethyl groups, such as a trifluoro methyl group.

In addition, in another embodiment, one of R₃ through R₆ (for exampleR₆) and one of R₇ through R₁₁ (for example R₇) may combine to form asingle bond between the phenyl rings, such that the emissive metalcomplex is represented by Formula 3.

Substituting the phenyl rings with at least one substituent group, asdiscussed above, may enable fine tuning of the emission properties ofthe resulting complex. For example, emission efficiency may be tuned byincluding an electron donating or electron withdrawing group on thearene backbone of the PN ligand. Nonlimiting examples of such groupsinclude methyl groups and trifluoromethyl groups.

According to one embodiment, the PN ligand may be prepared bynucleophilic attack of LiP^(i)Pr₂ (^(i)Pr=isopropyl) onfluorine-substituted diarylamine precursors. One nonlimiting example ofsuch a fluorine-substituted diarylamine precursor is1-fluoro-diphenylamine, which, after nucleophilic attack of LiP^(i)Pr₂,provides [PN]Li (shown in Reaction Scheme 1 below). A related PN ligandmay be prepared having phenyl, rather than isopropyl, substituents atthe P site, as noted above.

The L₁ and L₂ ligands may each independently be a substituentrepresented by PX₃, where each X group may be any hydrocarbonsubstituent. Nonlimiting examples of suitable hydrocarbon substituentsfor X include alkyl groups, alkenyl groups, alkynyl groups, aryl groups,heteroaryl groups, and the like. In one embodiment for example, each Xgroup is a methyl or phenyl group, such that the emissive metal complexis represented by either Formula 4 or Formula 5.

According to another embodiment of the present invention, the L₁ and L₂ligands together comprise a single, second PN ligand, i.e. L₁+L₂=a PNligand. According to this embodiment, the emissive metal complex isrepresented by Formula 6A.

In Formula 6A, each of the four phenyl rings are shown without theircorresponding R groups for clarity. However, both PN ligands includephenyl rings with R groups as discussed above with respect to Formula 1.In addition, in Formula 6A, the R groups on the phenyl rings in thesecond PN ligand are the same as the R groups R₃ through R₁₁, discussedabove in connection with Formula 1.

In another embodiment, the L₁ and L₂ ligands together comprise a singleDPPE (1,2-(diisopropylphosphino)ethane) ligand, i.e. L₁+L₂=DPPE.According to this embodiment, the emissive metal complex is representedby Formula 6B.

In Formula 6B, the phenyl rings on the PN ligand are shown without theircorresponding R groups for clarity. However, the PN ligand may includephenyl rings with R groups as discussed above with respect to Formula 1.In addition, any of the phenyl rings on the DPPE ligand may besubstituted at any position with any suitable substituent. Anysubstituent suitable for the R₃ through R₁₁ groups on the PN ligand arealso suitable for substituents on the phenyl rings of the DPPE ligand.

According to one embodiment of the present invention, a monomeric Cucomplex may be synthesized according to the following Reaction Scheme 1.In Reaction Scheme 1, a simple PN ligand having isopropyl substituentsat the P site is used. However, any other PN ligand may be used inReaction Scheme 1. In addition, Reaction Scheme 1 depicts the synthesisof a monomeric Cu complex, but similar Reaction Schemes may be used tosynthesize monomeric complexes of other metals, such as other d¹⁰ metals(e.g., Zn and Ag).

[PN]Li, shown in Reaction Scheme 1, exhibits blue luminescence whenirradiated with a UV lamp, and features an optical spectrum withtransitions at 411 nm, 354 nm and 286 nm. As shown in Reaction Scheme 1,the [PN]Cu[L]₂ complex may be prepared by adding diethyl ether solutionsof [PN]Li to a stirring suspension of CuBr.Me₂S and the appropriatetertiary phosphine. The resulting Cu complexes are bright yellow incolor.

Cu complexes represented by Formulae 4, 5 and 6B may be synthesizedaccording to Reaction Scheme 1. To prepare complexes with differentligands (L1 and L2), the proper tertiary phosphine (PR₃) is selected as2 L. Specifically, to prepare the complex of Formula 4, L is P(CH₃)₃. Toprepare the complex of Formula 5, L is P(Ph)₃. To prepare the complex ofFormula 6B, 2 L is DPPE.

Also, the complex of Formula 3 may be prepared according to a reactionscheme similar to Reaction Scheme 1. In particular, the reaction schemebegins with a [PN]Li precursor in which the two phenyl rings are fused,as shown in Formula 3. The rings of the [PN]Li precursor may be fused byany suitable means, and in one embodiment the rings are fused via aGoldberg coupling. After preparing a [PN]Li precursor having fusedphenyl rings, the compound represented by Formula 3 is producedaccording to Reaction Scheme 1.

To prepare complexes of other metals, for example Ag and Zn, theCuBr.Me₂S solution is replaced with a suitable solution for preparingcomplexes of the desired metal. For example, to prepare an Ag complex ofFormula 5, AgOTF and diethyl ether are used. As another example, a Zncomplex of Formula 6A may be prepared using ZnCl₂ and THF(tetrahydrofuran). More specific examples of the synthesis of variousexemplary complexes of the invention are described in the belowExamples.

EXAMPLES

The following Examples are presented for illustrative purposes only andare not to be construed as limiting the scope of the present invention.In the Examples, all manipulations were carried out using standardSchenk or glove-box techniques under a dinitrogen atmosphere. Unlessotherwise noted, solvents were deoxygenated and dried by thoroughsparging with N₂ followed by passage through an activated aluminacolumn. Non-halogenated solvents were tested with a standard purplesolution of sodium benzophenone ketyl in tetrahydrofuran in order toconfirm effective oxygen and moisture removal. Deuterated solvents weredegassed and stored over activated 3-Å molecular sieves prior to use.THF-d₈ was dried by passage over activated alumina and stored overactivated sieves prior to use. LiP(^(i)Pr)₂ was prepared according toknow procedures. All other reagents were purchased from commercialvendors and used without further purification, unless explicitly statedotherwise. NMR spectra were recorded at ambient temperature on a VarianMercury 300 MHz or Inova Automated 500 MHz spectrometer. ¹H NMR chemicalshifts were referenced to residual solvent. ³¹P NMR chemical shifts arereported relative to an external standard of 85% H₃PO₄. ¹⁹F NMR chemicalshifts are reported relative to either a HCF₃ or C₆F₆ standard. UV-vismeasurements were taken on a Varian Cary 50 Bio Spectrophotometer, usinga quartz crystal cell with a Teflon stopper. Electrochemical analysiswas performed on a CHI 600B Potentiostat/Galvanostat using a glassycarbon working electrode, a platinum wire auxiliary electrode, and aAg/AgNO₃ (0.01 M) reference electrode filled with THF, with reference toFc/Fc⁺ as an internal standard. X-ray diffraction studies were carriedout on a Bruker Smart 1000 CCD diffractometer.

One precursor material used in the following Examples was2-fluoro-diphenylamine, and was prepared as follows. In a glovebox, a200 mL Teflon-stopped high-pressure flask was charged with Pd₂dba₃ (315mg, 0.344 mmol; dba=dibenzylideneacetone), DPPF (275 mg, 0.688 mmol;DPPF=1,1′-bis(diphenylphosphino)ferrocene), NaO^(t)Bu (4.62 g, 48.16mmol), and 80 mL toluene. The reaction flask was removed from theglovebox, and 1-bromo-2-fluorobenzene (3.74 mL, 34.4 mmol) and aniline(3.14 mL, 34.4 mmol) were added by syringe under N₂ counterflow. Themixture was heated in an oil bath at 100° C. overnight. After verifyingconsumption of starting materials by gas chromatography-massspectrometry (“GC-MS”) and ¹⁹F NMR, the mixture was cooled and filteredthrough a plug of silica, and washed with copious amounts of petroleumether to yield a light yellow solution. The solvents were removed invacuo, yielding the desired product as a pale orange oil (5.49 g, 85%).(¹H NMR (C₆D₆, 300 MHz): δ 7.15-6.95 (m, 3H, Ar—H), 6.89-6.65 (m, 4H,Ar—H), 6.5 (m, 2H, Ar—H), 5.36 (br, 1H, NH); ¹⁹F NMR (282 MHz): δ−132.5. HRMS (EI⁺) m/z calculated for C₁₂H₁₀FN: 187.0797. Found:187.0796 [M⁺], 168.0947 [M-F]).

Another precursor material used in the following Examples was2-fluoro-5-methyl-diphenylamine, and was prepared as follows. In aglovebox, a 200 mL high-pressure reaction vessel was charged with 30 mLtoluene, Pd₂dba₃ (91.7 mg, 0.10 mmol), and2-(dicyclohexylphosphino)biphenyl (140.2 mg, 0.40 mmol). The reactionflask was then removed from the box and stirred, with the dark redmixture turning more orange. As the reaction flask was stirring,2-Fluoro-5-methylaniline (3.01 g, 24.05 mmol), iodobenzene (4.09 g,20.04 mmol), and dry toluene were added to a 50 mL Schlenk flask, whichwas then boil-degassed. After subsequent cannula transfer of theorganics into the high-pressure vessel, NaO^(t)Bu (2.70 g, 28.05 mmol)was added under N₂ counterflow, and the flask was sealed with a Teflonstopper. The mixture was heated to 110° C. for 20 hours, was allowed tocool to room temperature, was then filtered through a plug of silica,and washed with copious amounts of petroleum ether (about 250 mL). Thesolvent was removed, yielding an orange-brown oil. The crude product waspurified by column chromatography on silica gel with petroleum ethereluent, yielding 2-fluoro-5-methyl-diphenylamine as a pale yellow oil(3.01 g, 70%). (¹H NMR (CDCl₃, 300 MHz): δ 7.31 (t, 2H), 7.12 (d, 3H),7.00 (m, 2H), 6.64 (t, 1H), 6.75 (bs, 1H, NH), 2.27 (s, 3H, —CH₃). ¹⁹FNMR (282 MHz): δ −137.59 (s, 1F). HRMS (EI⁺) m/z calcd. for C₁₃H₁₂FN:201.0954. Found: 201.0957 [M⁺]).

Example 1 Lithium-2-(diisopropylphosphino)diphenylamide (StartingMaterial)

A 1.6 M hexane solution of nBuLi (7.75 mL, 12.35 mmol) was added to a200 mL Teflon-stopped flask charged with 20 mL of a light brown THFsolution of 1-Fluoro-diphenylamine (2.20 g, 11.76 mmol). The mixturethen turned orange and was stirred for 20 minutes. After concentrationto 5 mL, a 50 mL solution of LiP(iPr)₂ (2.92 g, 23.52 mmol) in THF wasadded, and the vessel was removed from the glove-box and heated to 65°C. for 8 days, monitored by GC-MS and ¹⁹F NMR. The mixture turned darkgreen over time, and emitted blue luminescence under a UV lamp. When noremaining starting materials were detected spectroscopically, themixture was brought back into the glove-box, and quenched with 5 mLEtOH. After addition of 40 mL petroleum ether, the reaction mixture wasfiltered through celite, and the solvents were removed in vacuo. As itwas concentrated, the oily residue formed large sticky bubbles, and themixture was repeatedly treated with diethyl ether and thenre-concentrated to control the bubbling. The residual oil was extractedwith petroleum ether, and filtered through a plug of silica. Removal ofsolvents left a brown oil that solidified when left at ambienttemperatures overnight, and was determined to be about 80% [PN]H by NMR,with an unknown phosphine-containing product as an impurity. Addition ofnBuLi (7.35 mL, 11.76 mmol) to a stirring solution of the brown solidsresulted in immediate precipitation of the compound represented byFormula 7 (below), which was isolated on a sintered glass frit, andwashed with copious amounts of petroleum ether before being collected asa spectroscopically pure, thermally unstable off-white powder (2.15 g,64%). (¹H NMR (300 MHz, THF-d⁸): δ 7.04 (m, 1H, Ar—H), 6.88 (m, 3H,Ar—H), 6.73 (m, 3H, Ar—H), 6.26 (t, 1H, Ar—H), 6.12 (t, 1H, Ar—H), 2.02(m, 2H, CH(CH₃)₂), 1.11, (q, 6H, CH(CH₃)₂), 0.98 (q, 6H, CH(CH₃)₂). ³¹PNMR (120 MHz): δ −6.03 (q, 1P). HRMS (EI⁺) m/z calculated for C₁₈H₂₄NP([PN]H): 285.1646. Found: 285.1637 [M⁺], 243.1072 [M-^(i)Pr], 200.0424[M-2^(i)Pr]).

Example 2 [PN]Cu(PPh₃)₂

A diethyl ether solution (about 3 mL) of CuBr.Me₂S and PPh₃ were cooledto −35° C. The PPh₃-containing solution was added to the CuBr.Me₂Ssuspension and the mixture was stirred and protected from the light withaluminum foil. After 5 minutes, a cooled (−35° C.) diethyl ethersolution of the compound prepared according to Example 1 was addedslowly to the reaction mixture, and the solution turned bright yellowimmediately. After 2 hours of stirring, the mixture was green-yellow,and the solvent was removed in vacuo. Extraction with benzene, followedby filtration through celite, yielded a bright yellow solution, whichwas lyophilized, affording a spectroscopically pure compound accordingto Formula 8 (below) as a yellow powder. X-Ray quality crystals weregrown from vapor diffusion of a solution of the resulting compound indiethyl ether with petroleum ether. (¹H NMR (C₆D₆, 300 MHz): δ 7.3 (m,30H, P(C₆H₅)₃), 7.02 (t, 2H, Ar—H), 6.92 (t, 3H, Ar—H), 6.79 (t, 1H,Ar—H), 6.72 (t, 1H, Ar—H), 6.59 (t, 1H, Ar—H), 6.17 (t, 1H, Ar—H), 2.26(sept., 2H, CH(CH₃)₂), 1.08 (dd, 6H, CH(CH₃)₂), 0.99 (dd, 6H, CH(CH₃)₂).¹³C NMR (75 MHz): δ 166.41, 158.39, 136.03 (d, J_(PC)=12.6 Hz), 134.61(d, J_(PC)=16.9 Hz), 133.34, 132.43, 129.81, 129.76, 129.14 (d,J_(PC)=8.3 Hz), 128.93, 126.05, 119.70, 113.40 (d, J_(PC)=156 Hz), 23.85(d, J_(PC)=12.31 Hz), 20.22 (d, J_(PC)=10.87 Hz), 19.02 (d, J_(PC)=3.0Hz). ³¹P NMR (120 MHz): δ −1.2 (br, 2P), −3.7 (br, 1P). Anal. calcd. forC₅₄H₅₃CuNP₃ C, 74.34; H, 6.12; N, 1.61; Found: C, 74.31; H, 5.94; N,1.60).

Example 3 [PN]Cu(PMe₃)₂

A diethyl ether solution (about 3 mL) of CuBr.Me₂S and P(CH₃)₃ werecooled to −35° C. The P(CH₃)₃-containing solution was added to theCuBr.Me₂S suspension and the mixture was stirred and protected from thelight with aluminum foil. After 5 minutes, a cooled (−35° C.) diethylether solution of the compound prepared according to Example 1 was addedslowly to the reaction mixture, and the solution turned bright yellowimmediately. After 2 hours of stirring, the mixture was green-yellow,and the solvent was removed in vacuo. Extraction with benzene, followedby filtration through celite, yielded a bright yellow solution, whichwas lyophilized, affording a spectroscopically pure compound accordingto Formula 9 (below) as a yellow powder. X-Ray quality crystals weregrown from a vapor diffusion of a diethyl ether solution of theresulting compound with petroleum ether. (¹H NMR (C₆D₆, 300 MHz,): δ7.72 (q, 1H, Ar—H), 7.4 (m, 2H, Ar—H), 7.29 (t, 2H, Ar—H), 7.2-7.0 (m,2H, Ar—H), 6.78 (tt, 1H, Ar—H), 6.54 (t, 1H, Ar—H), 1.95 (sept., 2H,CH(CH₃)₂), 1.10 (q, 6H, CH(CH₃)₂), 1.00 (q, 6H, CH(CH₃)₂), 0.85 (br.18H, P(CH₃)₃). ¹³C NMR (125 MHz): δ 163.40, 158.20, 131.80, 130.65,128.79, 128.19, 121.20, 117.63 (d, J_(PC)=34.9 Hz), 114.95, 114.07 (dd,J_(PC)=478.5 Hz, 3.7 Hz), 22.45 (d, J_(PC)8.8 Hz), 19.63 (d, J_(PC)=11.6Hz), 18.41 (d, J_(PC)=3.3 Hz), 16.63 (d, J_(PC)=13.0 Hz).³¹P NMR (120MHz): δ 7.0 (br, 1P, [PN]), −46.3 (br, 2P, P(CH₃)₃). Anal. calcd. forC₂₄H₄₁CuNP₃ C, 57.64; H, 8.26; N, 2.80; Found: C, 57.61; H, 8.00; N,2.84).

Example 4 [PN]CuDPPE

A diethyl ether solution (about 3 mL) of CuBr.Me₂S and DPPE(1,2-bis(diphenylphosphino)ethane) were cooled to −35° C. TheDPPE-containing solution was added to the CuBr.Me₂S suspension and themixture was stirred and protected from the light with aluminum foil.After 5 minutes, a cooled (−35° C.) diethyl ether solution of thecompound prepared according to Example 1 was added slowly to thereaction mixture, and the solution turned bright yellow immediately.After 2 hours of stirring, the mixture was green-yellow, and the solventwas removed in vacuo. Extraction with benzene, followed by filtrationthrough celite, yielded a bright yellow solution, which was lyophilized,affording a spectroscopically pure compound according to Formula 10(below) as a yellow powder. Crystals used for X-Ray diffraction weregrown from vapor diffusion of petroleum ether and a solution of theresulting product in THF. (¹H NMR (C₆D₆, 300 Mhz,): δ 7.65 (q, 2H,Ar—H), 7.44 (m, 8H, DPPE), 7.2-7.1 (m, 2H, Ar—H), 7.02 (d, 12H, DPPE),6.9 (m, 3H, Ar—H), 6.55 (m, 2H, Ar—H), 2.18 (t, 4H, DPPE), 2.08 (sept.,2H, CH(CH₃)₂), 1.15 (q, 6H, CH(CH₃)₂), 0.89 (q, 6H, CH(CH₃)₂). ¹³C NMR(125 MHz): δ 159.27, 136.06, 133.82 (t, J_(PC)=8.1 Hz), 133.18, 131.53,129.26, 129.09 (t, J_(PC)=4.3 Hz), 124.15, 117.03, 114.20 (dd,J_(PC)=571.3 Hz, 4.7 Hz), 68.16 (THF), 27.36 (td J_(PC)=17.1 Hz, 5.5Hz), 26.16 (THF), 23.09 (d, J_(PC)=11.9 Hz), 19.89 (d, J_(PC)=11.1 Hz),17.97. ³¹P NMR (120 Mhz): δ 8.7 (br, 1P, [PN]), −1.4 (br 2P, DPPE).Anal. calcd. for C₄₄H₄₇CuNP₃ C, 70.81; H, 6.35; N, 1.88; Found: C,70.52; H, 6.46; N, 1.60).

Example 5 [^(Me)PN]Li (Starting Material)

A 10 mL THF solution of 2-fluoro-5-methyldiphenylamine (1.452 g, 5.19mmol) was cooled to −35° C. and added to a 100 mL high pressure flask.To this vessel was added a 1.6 M solution of nBuLi in hexane (3.41 mL,5.45 mmol), dropwise with stirring. The clear colorless solution turnedyellow, then orange, as it was warmed to room temperature, after whichit was stirred for 2 hours. A 10 mL THF solution of LiP(iPr)₂ (1.611 g,12.99 mmol) was added slowly to the mixture, and the vessel was sealedwith a Teflon stopper, removed from the glovebox, and heated to 80° C.for 7 days. After this time, a GC-MS trace showed complete consumptionof the starting material and growth of one other peak corresponding tothe product. The flask was brought back into the glovebox, and thereaction was quenched with 5 mL EtOH, resulting in a pale green color,before removal of solvents. Filtration of the residue through silica,washing with copious amounts of petroleum ether, followed by removal ofsolvents in vacuo and another filtration through celite, yielded[^(Me)PN]Li as a mixture with another phosphorous-containing product(80% by 31P NMR integration). Addition of nBuLi (3.41 mL, 5.45 mmol) toa cooled (−35° C.) solution of this crude product in a solution of 10 mLpetroleum ether resulted in immediate precipitation of beige solids. Themixture was stirred for 2.5 hrs before collecting the solids on a frit,and washing with 60 mL petroleum ether, affording pure [^(Me)PN]Li, acomplex according to the following Formula 11. (¹H NMR (THF-d⁸, 300Mhz): δ 6.7-6.9 (m, 6H), 6.25 (t, 1H), 5.98 (d, 1H), 1.96-2.06 (m, 5H,Ar—CH₃, CH(CH₃)₂), 1.10 (dd, 6H), 0.95 (d, 6H). ³¹P NMR (120 MHz): δ−7.07 (m, 1H). HRMS (EI⁺) m/z calcd. for C₁₉H₂₆NP: 299.1805. Found:299.1803 [M⁺], 257.1387 [M-^(i)Pr], 214.0860 [M-2^(i)Pr]).

Example 6 [^(CF3)PN]Li (Starting Material)

In the glovebox, 1-Fluoro-4-trifluoromethyl-diphenylamine (1.94 g, 7.63mmol) was dissolved in 20 mL THF, and added to a 200 mL Teflon-stoppedglass vessel equipped with a stirbar. The vessel was cooled to −78° C.,at which point a 1.6 M hexane solution of nBuLi (4.8 mL, 7.71 mmol) wasadded dropwise by syringe. The reaction mixture was allowed to warmwhile stirring for 30 minutes, during which time the solution darkenedfrom pale orange to a darker orange-brown. At this point, a 10 mL THFsolution of LiP(iPr)₂ (1.90 g, 15.33 mmol) was added to the reactionmixture, and the vessel was heated to 70° C. for 4 days, whilemonitoring the reaction for completion by GC-MS and ³¹P NMR. Thereaction mixture, which had darkened to a red-brown, emitted yellowluminescence under a UV lamp. The vessel was cooled to room temperature,and was brought into the glovebox. The mixture was then quenched with 10mL EtOH, and 10 mL of petroleum ether were added, yielding agolden-brown solution. The solvents were removed in vacuo. The oilyresidue was treated with 10 mL of diethyl ether, which was subsequentlyremoved under reduced pressure; this procedure was repeated as necessaryto reduce bubbling. The residue was extracted with petroleum ether,filtered through celite, and concentrated to a brown oil, which was leftunder dynamic vacuum overnight. The residue contained a mixture of[^(CF3)PN]H (about 85-90%) and one unknown P-containing side-product (δ+4 ppm). Crude [^(CF3)PN]H was dissolved in 20 mL of petroleum ether,added to a 100 mL round-bottom flask, and cooled to −35° C. A 1.6 Mhexane solution of nBuLi (4.8 mL, 7.71 mmol) was then added dropwise bysyringe, yielding a beige precipitate. The flask was warmed to roomtemperature and stirred overnight, at which point the solids werecollected on a sintered glass frit, and washed with 40 mL petroleumether, yielding spectroscopically pure [^(CF3)PN]Li (1.61 g, 59%),having the following Formula 12. (¹H NMR (THF-d⁸, 300 MHz): δ 7.15 (d,1H), 7.05-6.94 (m, 3H), 6.82 (dd, 2H), 6.45 (t, 1H), 6.24 (dd, 2H), 2.09(sept, 2H, CH(CH₃)₂), 1.14 (q, 6H, CH(CH₃)₂), 1.00 (q, 6H, CH(CH₃)₂).³¹P NMR: δ −6.6 (br q, 1P). ¹⁹F NMR: δ −60.5 (s, 3F). HRMS (EI⁺) m/zcalcd. for C₁₉H₂₃F₃NP: 353.1520. Found: 353.1506 [M⁺], 311.1105[M-^(i)Pr], 268.0594 [M-2^(i)Pr], 235.0692 [M-(^(i)Pr)₂P]).

Example 7 [^(Me)PN]Cu(PPh₃)₂

Diethyl ether solutions of the compound prepared according to Example 5(67.7 mg, 0.222 mmol), CuBr.Me₂S (45.6 mg, 0.222 mmol), and PPh₃ (116.3mg, 0.444 mmol) were cooled to −35° C. PPh₃ was added to the coldsuspension of CuBr.Me₂S while stirring, and the scintillation vial wascovered with aluminum foil. After 5 minutes the compound preparedaccording to Example 5 was added slowly, and the reaction mixture wasstirred for 2.5 hrs. After removal of solvent in vacuo, the residue wasextracted with benzene, filtered through celite, and lyophilized,yielding [^(Me)PN]Cu(PPh₃)₂ (represented by Formula 13 below) in aquantitative yield as a yellow powder. X-Ray quality crystals were grownfrom a diethyl ether solution of the resulting product layered withpetroleum ether and cooled to −30° C. (¹H NMR (C₆H₆, 300 MHz): δ7.48-7.35 (m, 12H, P(C₆H₅)₃), 7.26 (d, Ar—H), 7.2-7.1 (m), 7.08-7.0 (m,18H, P(C₆H₅)₃), 6.86 (t, 1H, Ar—H), 6.42 (d, 1H, Ar—H), 2.11 (s, 3H,[CH3PN]), 2.06 (sept, 2H, CH(CH₃)₂), 1.1-0.94 (m, 12H, CH(CH₃)₂). ¹³CNMR (75 MHz): δ 166.54, 158.34, 141.69, 135.80 (d, J_(PC)=12.0 Hz),134.18 (d, J_(PC)=17.2 Hz), 132.98, 129.51, 128.87 (d, J_(PC)=8.3 Hz),125.88, 119.35, 114.05 (dd, J_(PC)=75.3 Hz, 4.9 Hz), 23.51 (d,J_(PC)=13.1 Hz), 22.15, 19.92 (d, J_(PC)=11.2 Hz), 18.67 (d, J_(PC)=3.7Hz). ³¹P NMR (120 MHz): δ 1.1 (2P), −3.9 (1P). Anal. calcd. forC₅₅H₅₅CuNP₃ C, 74.52; H, 6.25; N, 1.58. Found: C, 74.42; H, 6.45; N,1.57).

Example 8 [^(CF3)PN]Cu(PPh₃)₂

Diethyl ether solutions of the compound prepared according to Example 6(97.8 mg, 0.273 mmol), CuBr.Me₂S (56.0 mg, 0.273 mmol), and PPh₃ (142.9mg, 0.545 mmol) were cooled in scintillation vials to −35° C. PPh₃solution was added to the slurry of CuBr.Me₂S before the vial wascovered with aluminum foil and stirred for 5 minutes. The compoundprepared according to Example 6 was slowly added to the slurry viapipette, which immediately resulted in a clear yellow solution. Thereaction was stirred for 2 hr, at which point the solvents were removedin vacuo. The residues were extracted with benzene, and filtered throughcelite, yielding a bright yellow solution. The benzene was removed bylyophilization overnight, affording a spectroscopically pure yellowpowder of [^(CF3)PN]Cu(PPh₃)₂ (represented by Formula 14 below) (254.6mg, 99%). X-Ray quality crystals were grown from a cooled (−30° C.)layering of petroleum ether upon a diethyl ether solution of theresulting product. (¹H NMR (C₆D₆, 300 Mhz): δ 7.65 (d, 1H, [PN]Ar—h),7.4 (m, 12H, P(C₆H5)₃), 7.29 (d, 2H, [PN]Ar—H), 7.08 (t, 3H, [PN]Ar—h),7.0 (m, 18 H, P(C₆H₅)₃), 6.83 (t, 1H, [PN]Ar—H), 6.76 (d, 1H, [PN]Ar—H),1.933 (sept., 2H, CH(CH₃)₂), 0.977 (dd, 6H, CH(CH₃)₂), 0.873 (dd, 6H,CH(CH₃)₂). ¹³C NMR (125 MHz): δ 135.64 (d, J_(PC)=15.6 Hz), 134.54 (d,J_(PC)=17.09), 133.35, 129.59, 129.97 (d, J_(PC)=0.9 Hz), 129.20 (d,J_(PC)=8.3 Hz), 128.92 (d, J_(PC)=0.4 Hz), 125.42, 120.57, 109.41,106.95, 23.86 (d, J_(PC)=12.4 Hz), 20.11 (d, J_(PC)=11.1 Hz), 18.91 (d,J_(PC)=3.1 Hz). ³¹P NMR (120 MHz): δ 0.19 (br, 2P, P(C₆H₅)₃), −3.98 (br,1P, [PN]). 19 F NMR (470 MHz): −63.4 (3F). Anal. calcd. forC₅₅H₅₂CuF₃NP₃ C, 70.24; H, 5.57; N, 1.49. Found: C, 70.10; H, 5.84; N,1.45).

Example 9 [PN]Ag(PPh₃)₂

A 20 mL scintillation vial protected from the light was charged withAgOTf and 3 mL diethyl ether. To the stirring solution was added adiethyl ether solution of PPh₃, and five minutes subsequently was addeda solution of the compound prepared according to Example 1. After 2hours, the reaction mixture was filtered, and the bright yellow solutionwas dried in vacuo. The resulting product was [PN]Ag(PPh₃)₂ (representedby the following Formula 15). Analytically pure crystals were grown froma THF solution layered with petroleum ethers, and cooled to −30° C. (¹HNMR (C₆D₆, 300 MHz): δ 7.71 (t, 1H, Ar—H), 7.49 (d, 2H, Ar—H), 7.38 (m,12H, P(C₆H₅)₃), 7.2-7.1 (m, 4H, Ar—H), 7.05 (m, 18H, P(C₆H₅)₃), 6.77 (t,1H, Ar—H), 6.55 (t, 1H, Ar—H), 2.02 (sept., 2H, CH(CH₃)₂), 1.08 (q, 6H,CH(CH₃)₂), 0.93 (q, 6H, CH(CH₃)₂). ¹³C NMR (75 MHz): δ 159.2, 135.49 (d,J_(PC)=12.9 Hz), 134.70 (d, J_(PC)=17.5 Hz), 133.58, 131.82, 130.02,129.70, 129.24 (d, J_(PC)=8.59 Hz), 123.67, 116.88, 113.43 (d,J_(PC)=33.2 Hz), 114.04 (d, J_(PC)=342.2 Hz), 23.92 (d, J_(PC)=7.44 Hz),20.48 (d, J_(PC)=12.31), 19.23 (d, J_(PC)=4.87 Hz). ³¹P NMR (120 MHz): δ7.7 (1P), 5.5 (2P). Anal. Calcd. for C₅₄H₅₃AgNP₃ C, 70.74; H, 5.83; N,1.53. Found: C, 70.67; H, 6.03; N, 1.51).

Example 10 [PN]₂Zn

To a THF solution of ZnCl₂ (16.0 mg, 0.1174 mmol in 3 mL) chilled to−35° C. in a scintillation vial, was added 2 equivalents of the compoundprepared according to Example 1 (68.4 mg, 0.235 mmol) in 5 mL cold THFsolution, while stirring. The mixture was allowed to warm to roomtemperature while stirring for 3 hours. The golden reaction solution wasthen filtered through celite, dried by evaporation, and extracted withdiethyl ether. Filtration through celite, followed by washing with 2 mLether, yielded a golden yellow solution that was layered with petroleumether and cooled to −30° C., affording golden crystals of analyticallypure [PN]₂Zn (represented by Formula 16 below). (¹H NMR (C₆D₆, 300 MHz):δ 7.2-7.1 (m, 4H), 7.08-6.9 (m, 10H), 6.61 (t, 2H), 6.25 (m, 2H), 2.36(sept, 4H, CH(CH₃)₂), 1.28 (q, 6H, CH(CH₃)₂), 1.18 (q, 6H, CH(CH₃)₂),1.02 (q, 6H, CH(CH₃)₂), 0.36 (q, 6H, CH(CH₃)₂). ¹³C NMR: δ 162.87 (t,J_(PC)=7.8 Hz), 154.62, 132.77 (d, J_(PC)=6.4 Hz), 129.87, 124.62,120.69, 115.14, 113.26, 107.85 (t, J_(PC)=21.2 Hz), 23.46 (t, J_(PC)=7.4Hz), 21.19 (t, J_(PC)=10.5 Hz), 19.35 (t, J_(PC)=3.6 Hz), 18.86 (t,J_(PC)=4.1 Hz), 17.96 (t, br), 16.69 (s, br). ³¹P NMR (120 MHz): δ−12.23 (2P). Anal calcd. for C₃₆H₄₆ZnN₂P₂ C, 68.19; H, 7.31; N, 4.42.Found: C, 68.47; H, 7.50; N, 4.04).

Testing and Measurement

The compounds prepared according to Examples 1 through 10 were subjectedto the following testing and measurement procedures.

X-Ray Crystallography

X-ray quality crystals were grown for each complex. The crystals weremounted on a glass fiber with Paratone-N oil. Structures were determinedusing direct methods with standard Fourier techniques using the BrukerAXS software package. In some cases, Patterson maps were used in placeof the direct methods procedure.

Lifetime Measurements

A solution of analyte in diethyl ether or benzene was prepared in anitrogen filled glovebox. The quartz cuvettes (1 cm pathlength) werecharged with this solution, and sealed with a Teflon stopper. Absorptionspectra were acquired both before and after measurements to ensure thesample was not photodegrading. Generally, there was an insignificantamount (<1%) of photodecomposition under the experimental conditions,although there was more pronounced degradation under prolongedirradiation. Luminescence lifetime measurements were carried out using 8ns pulses (at a repetition rate of 10 Hz) from a Nd:YAG laser pumped OPO(Quanta Ray Pro, Spectra Physics). The luminescence was dispersedthrough a monochromator (Instruments SA DH-10) onto a photomultipliertube (PMT) (Hamamatsu R928). The PMT current was amplified and recordedwith a transient digitizer (Lecroy 9354A). Measurements were performedat 298 K with two cuvettes of analyte solution, with excitation atλ_(ex)=430 nm for the compounds prepared according to Examples 2, 3, 4,7 and 8, excitation at λ_(ex)=440 nm for the compound prepared accordingto Example 9, and excitation at λ_(ex)=310 nm for the compounds preparedaccording to Examples 1 and 10. Emission was collected at thewavelength, λ_(em), specified in Table 1, below. The emission decay wasaveraged over at least 500 laser pulses, and fit to an exponentialfunction from which k_(obs) and τ were determined. For the compoundsprepared according to Examples 3 and 8, the short-lived portion of thebi-exponential function was below the response time of the amplifier,and is approximated at <10 ns. The Zn complex prepared according toExample 6 also had a lifetime that was too short to quantify, and so isestimated simply as <10 ns. TABLE 1 Data for Excited State LifetimeMeasurements. Sample λ_(em (nm)) k_(obs) (s⁻¹) Lifetime (τ) (μs) 223 μMExample 1 in 480 8.64 × 10⁷ 0.012 (1)  Et₂O 40.3 μM Example 2 504 4.94 ×10⁴ 20.2 (1) in C₆H₆ 80.0 μM Example 3 503 (a) 4.44 × 10⁴ 22.3 (7) inC₆H₆ (b) n/a <10 ns 77.7 μM Example 4 533 6.15 × 10⁴ 16.3 (3) in C₆H₆98.1 μM Example 9 517 8.76 × 10⁶ 0.125 (5)  in C₆H₆* 49.6 μM Example 7504 1.50 × 10⁵  6.7 (1) in C₆H₆ 57.4 μM Example 8 555 (a) 6.76 × 10³ 150 (3) in C₆H₆* (b) n/a <10 ns*= Sample was excited at 440 nm.Oxidative Luminescence Quenching

Samples were prepared from two stock solutions: 34 μM Example 2 in C₆H₆,and a mixture of 34 μM Example 2 and 339 μM 2,6-dichlorobenzoquinone(DCQ). Using cuvettes with Teflon-separated 25 mL bulbs, solutions ofvarying concentrations were prepared in the cuvette, with the stocksolution of Example 2 in the bulbs. After measurements were made on thecuvette solution, the stock solution in the bulb was mixed with thecuvette solution, diluting the concentration by half. Luminescencelifetime measurements were taken. The data measurements are reported inTable 2, below and in FIG. 1, which is a Stem-Volmer plot of k_(obs) vs.concentration of DCQ indicating oxidative quenching of the compoundprepared according to Example 2 with 2,6-dibenzoquinone (Q). In FIG. 1,y=9.043×10⁹(x)+36767 and R²=0.9997. The data is consistent withdiffusion-limited electron transfer, with a rate constant of k=9.04×10⁹M⁻¹s⁻¹. TABLE 2 Data for Excited State Lifetime Measurements.Concentration of DCQ k_(obs) (s⁻¹) Lifetime (τ, 1/k_(obs)) (μs)   0 μM4.70 × 10 ⁴ 21.26 11.3 μM 1.34 × 10⁵ 7.48 22.6 μM 2.25 × 10⁵ 4.44 33.8μM 3.51 × 10⁵ 2.84 42.4 μM 4.29 × 10⁵ 2.33 68.7 μM 6.65 × 10⁵ 1.50 84.7μM 7.84 × 10⁵ 1.27 169.5 μM  1.57 × 10⁶ 0.635Quantum Yield Experiments

Emission spectra were recorded on a Spex Fluorolog-2spectro-fluorometer. A solution of analyte or reference compound inbenzene, diethyl ether, tetrahydrofuran, or acetonitrile was prepared ina nitrogen filled glovebox. Cuvettes (1 cm path length) were chargedwith this solution and sealed with a teflon stopper. The absorptionspectra were acquired both before and after fluorescence measurements toensure the sample was not degrading. In some cases, a very minor amount(<1%) of photodecomposition was observed, with more pronounceddegradation under prolonged exposure to light. Fluorescence measurementswere performed at the specified wavelength and corrected for detectorresponse after equilibration to 298 K. The area under the curve of theemission spectrum was determined using standard trapezoidal integrationmethods. Quantum yields were then calculated by known methods usingEquation I, below. The results are reported in Table 3, below. Quininesulfate in 0.1 N H₂SO₄ ³ (φ=0.54) and [Ru(bpy)₃][PF₆ ]in acetonitrile(φ=0.075) were used as reference standards.φ=(QR)(I/IR)(ODR/OD)(η²/η_(R) ²)   Equation I

In Equation 1, φ is the quantum yield of the sample, QR is the quantumyield of the reference, I is the integrated intensity of the analyte, IRis the integrated intensity of the reference, ODR is the optical densityof the reference in absorption units, OD is the optical density of theanalyte in absorption units, η is the index of refraction of the solventin which the analyte was dissolved, and η_(R) is the index of refractionof the solvent in which the reference was dissolved.

Lithium salts of the ligands were prone to photodecomposition.Specifically, the compounds prepared according to Examples 1 (decomposedby 10%), 5 (decomposed by 20%) and 6 (decomposed by 15%) all decomposedsignificantly after irradiation in the fluorimeter. The quantum yieldresults reported below are crude values, and are reported withconfidence of ±5 on the last significant figure for measurements inbenzene, and ±10 on the last two significant figures for measurements inEt₂O and THF. TABLE 3 Data for Quantum Yield Measurements. Sample(solvent) λ_(ex) φ^(a) Example 1 (Et₂O) 430 0.16 Example 2 (C₆H₆) 4300.56 350 0.52 Example 2 (Et₂O) 430 0.29 Example 2 (THF) 430 0.27 Example3 (C₆H₆) 430 0.21 350 0.17 Example 3 (Et₂O) 430 0.10 Example 3 (THF) 4300.05 Example 4 (C₆H₆) 430 0.31 350 0.36 Example 4 (Et₂O) 430 0.15Example 4 (THF) 430 0.05 Example 5 (Et₂O) 430 0.12 Example 6 (Et₂O) 4300.05 Example 7 (C₆H₆) 430 0.70 Example 7 (Et₂O) 430 0.55 Example 7 (THF)430 0.30 Example 8 (C₆H₆) 430 0.16 Example 8 (Et₂O) 430 0.08 Example 8(THF) 430 0.07 Example 9 (C₆H₆) 430 0.00106 Example 10 (C₆H₆) 350 0.088Photophysical Properties

The following Table 4 reports certain photophysical properties of thecompounds prepared according to Examples 1 through 10. In Table 4, λ(cm⁻¹) is the reorganization energy, and is calculated according toEquation 2, below.λ=(Δν_(1/2))²/(16RT ln 2)   Equation 2In Equation 2, Δν_(1/2) is the full width at half maximum, R is 8.31451J/mol·K, and T is 298 K.Results

X-ray diffraction analysis of the complexes prepared according toExamples 2, 3 and 4 confirm that the complexes have monomeric,pseudotetrahedral structures. FIG. 2 shows the structure of the complexprepared according to Example 2, and FIG. 3A shows the structure of thecomplex prepared according to Example 3. Cyclic voltammetry of thecomplex of Example 2 shows a reversible peak at −270 mV vs. Fc/Fc+ (SeeFIG. 4). The X-ray diffraction analysis of the complex preparedaccording to Example 4 confirmed an overall connectivity relate to thecomplexes prepared according to Examples 2 and 3. However, the structureof the complex of Example 4 suffered from twinning.

Absorption spectra for the complexes prepared according to Examples 2, 3and 4 (shown in FIG. 5) feature similar peaks around 430 nm(ε=2,000-2,500 M−1 cm−1) and 350 nm (ε=10,000 M−1 cm−1), along with morecomplicated higher energy transitions. The complexes prepared accordingto Examples 2, 3 and 4 glow bright green under visible light, both inthe solid state and in solution. Excitation into any absorption bandleads to sharp, featureless emission peaks at 298K, i.e. 504 nm for thecomplex of Example 2, 497 for the complex of Example 3, and 534 nm forthe complex of Example 4 (see FIG. 6). The quantum efficiency of eachcomplex in benzene solution at 298K was assessed with excitation at 430nm and 350 nm. The emission/excitation spectra for the complexes ofExamples 2, 3 and 4 are shown in FIGS. 5A, 5B and 5C, respectively.

As shown in the following Table 4, quantum yields of the complexes varywidely depending on the auxiliary ligand, from φ=0.56 for the complex ofExample 2, to φ=0.21 for the complex of Example 3. Such high solutionquantum efficiency is unique among monomeric Cu systems, as highlightedby the results listed in Table 4. When more polar solvents, such asdiethyl ether or THF are employed, the luminescence efficiency issignificantly attenuated, typically by about 50%. TABLE 4 PhotophysicalComparison of Cu Complexes at 298 K λ_(abs) λ_(em) Complex Solvent (nm)(nm) φ_(em) ^(a) τ (μs) Example 1 Et₂O 411 480 0.16  0.012(1) Example 2C₆H₆ 434 504 0.56  20.2(1) Example 3 C₆H₆ 427 497 0.21  22.3(7) Example4 C₆H₆ 423 534 0.32  16.3(3) Example 7 C₆H₆ 433 498 0.70  6.7(1) Example8 C₆H₆ 444 552 0.16 150(3) [dbpCuPOP]⁺ CH₂Cl₂ 378 560 0.16  16.1⁷ (dbp =2,9-di-n-butyl-1,10- phenanthroline; POP = bis[2-(diphenylphosphino)phenyl] ether) [dmpCudppe]⁺ CH₂Cl₂ 400 630 0.010 1.33⁷ (dmp = 2,9-dimethyl-1,10- phenanthroline) CuI(dppb)PPh₃ Me-THF˜380   550 0.01 <1^(Error! Bookmark not defined.) (dppb = 1,2-bis[diphenylphosphino] benzene)^(a)= quantum yields are reported with a confidence of ±5 on the lastsignificant figure;b = data reported in CH2Cl2;c = data reported in 2-methyl-tetrahydrofuran

The complexes of Examples 2, 3 and 4 show long luminescence lifetimes inbenzene solutions, i.e. 20.2(1) μs for Example 2 (see FIG. 6), 22.3(7)μs for Example 3, and 16.3(3) μs for Example 4. The lifetimes in Et2Owere virtually identical to those in benzene. The luminescence decay ofthe complex of Example 3 (PME₃ adduct) has two components, with a smallspike indicating the decay of a shorter-lived species (<10 ns; see Table1 above).

In Examples 5 and 6, two PN ligands with donating and withdrawing groupson the arene backbone were used to tune the emission frequency. Thecomplexes of Examples 5 (methyl substituted [^(Me)PN]Li) and 6 (CF₃substituted [^(CF3)PN]Li) were prepared analogously to the complex ofExample 1, with subsequent metalation in the present of 2 equivalents ofPPh3, yielding [^(Me)PN]Cu(PPh₃)₂ according to Example 7, and[^(CF3)PN]Cu(PPh₃)₂ according to Example 8. As shown in FIG. 7,methyl-substitution does not generally perturb the optical spectrum whencompared with the complex of Example 2, and only a 6 nm blue-shift isobserved for its emission maximum (as shown in FIG. 6). The complexaccording to Example 7 emits significantly brighter than that of thecomplex of Example 2, with Φ=0.70, and a concomitantly shorterluminescence lifetime of 6.7(1) μs. The emission/excitation spectra ofthe complex of Example 7 is shown in FIG. 7A.

As shown in FIG. 7, relative to the complex of Example 2,CF₃-substitution on the ligand backbone imparts a 10 nm red-shift in theoptical spectrum (λ_(max)=444 nm) for the complex of Example 8, which ismatched by a 48 nm red-shift in the emission maximum (see FIG. 6). Thequantum efficiency of the complex of Example 8 in benzene at 298K, withΦ=0.16, presents a substantial decrease compared to the complexes ofExamples 2 and 7 (PPh₃ adducts). As shown in FIG. 8, the polycrystallinecomplex of Example 8 displays structured emission at 77 K, and broademission at 298 K that closely resembles the room temperature solutiondata. The similar emission from crystalline and solution samples isconsistent with an unchanged structure in solution. However, there is adramatic increase in the measured luminescence lifetime, to 150(3) μs(see FIG. 6). As for the complex of Example 3 (PME₃ adduct), there is atwo-component decay profile, with a much more pronounced short-lived(<10 ns) species. These decay profiles reflect independentsinglet/triplet emission pathways. The triplet excited state species isnearly an order of magnitude longer-lived than dbpCu(POP), and may bethe longest-lived monomeric Cu emitter presently known in solution atambient temperature. The emission/excitation spectra of the complex ofExample 8 is shown in FIG. 7B.

The complex of Example 9 ([PN]Ag(PPh₃)₂) was prepared by adding thecomplex of Example 1 to AgOTF in the presence 2 equivalents of PPh3 indiethyl ether, affording a golden yellow complex. X-ray diffractionanalysis of the resulting product showed an analogous geometry to thecopper complex of Example 2 (see FIG. 3B). The complex of Example 9 is arare example of a mononuclear silver amide complex. While its absorptionspectrum (shown in FIG. 9) is similar to those of the complexes ofExamples 2 and 3, its emission spectrum (shown in FIG. 10) exhibits amuch broader peak at 544 nm, suggesting loss of energy via structuralreorganization. The luminescence is attenuated relative to thecorresponding Cu complexes (Φ=0.0010), and it has a lifetime that islikewise much shorter (125(5) ns).

Metathesis of two equivalents of the complex of Example 1 with ZnCl2,followed by filtration and crystallization according to Example 10,provided yellow [PN]₂Zn. Excitation at either absorption feature(λmax=324 nm, 390 nm) led to aquamarine blue emission centered at 475 nmthat was substantially less efficient and shorter lived than for the Cucomplexes (Φ=0.088; τ<10 ns). The absorption spectrum of the [PN]₂Zncomplex prepared according to Example 10 is shown in FIG. 9, and theexcitation/emission spectra are shown in FIG. 11.

Although the silver and zinc complexes exhibit useful luminescenceproperties, the use of copper enables access to the long-lived tripletexcited state. Also, in the absence of Cu, only fluorescence isobserved. An intraligand charge transfer (ILCT) transition may bepresent in all of the compounds prepared according to Examples 1 through10. Excitation from the N lone pair to arene π* is consistent with thecalculated HOMO and LUMO of the compound of Example 3, where substantialN lone pair character (mixed with non-bonding arene π character) ispresent in the HOMO, and a predominantly π* orbital is depicted in theLUMO (the HOMO and LUMO of the compound of Example 3 are shown in FIGS.3C and 3D respectively). Emission from this transition is manifested asshort-lived fluorescence for the non-copper-containing species ofExamples 1, 5, 6 and 10. However, the Cu emitters of Examples 2, 3, 4, 7and 8 seem to display both singlet and triplet emissions, indicative ofadditional luminescence properties.

Although one description of the observed Cu phosphorescence ismetal-to-ligand charge transfer (MLCT) from a Cu d-orbital to the areneπ* orbital, this description is inconsistent with the data. First, asshown in FIG. 9, only minor differences are observed in the absorptionspectra of Cu and Ag complexes of Examples 2 and 9, respectively, ratherthan the often striking shift in MLCT transition energy caused by movingto a 4d element. Second, there is minimal solvent dependence on theground state absorption spectrum of the complex of Example 2, as shownin FIG. 12, while significant solvent dependence is often observed inwell-defined MLCT systems. Third, MLCT states generally have largeStokes shifts, but the complexes here all have anomalously small Stokesshifts for MLCT. Finally, the Cu complexes do not appear to be quenchedby a five-coordinate exciplex, as is typical for MLCT. If exciplexquenching played a significant role, the differences in steric bulkbetween the compound of Examples 2, 3 and 4 might be expected to have amore significant effect on the phosphorescence lifetime. Electroniceffects seem to play a more important role when comparing the compoundof Examples 2, 7 and 8, as the sterically similar (but electronicallydiverse) complexes have quite different lifetimes and quantumefficiencies. Given this data, the Cu phosphorescence appears to bederived from good orbital overlap and energetic matching between the Cud-manifold and the ligand π* system, which allows facile intersystemcrossing to a Cu-stabilized triplet.

While the present invention has been illustrated and described withreference to certain exemplary embodiments, those of ordinary skill inthe art will understand that various modifications and changes may bemade to the described embodiments without departing from the spirit andscope of the present invention, as defined in the following claims.

1. A monomeric metal complex comprising a compound represented byFormula 1:

wherein: M is a d¹⁰ metal; each of R₁ and R₂ is a substituted orunsubstituted hydrocarbon substituent; each of R₃ through R₁₁ is asubstituted or unsubstituted hydrocarbon substituent; and each of L₁ andL₂ is independently selected from the group consisting of substituentsrepresented by PX₃, wherein X is a hydrocarbon substituent.
 2. Amonomeric metal complex according to claim 1, wherein M is selected fromthe group consisting of Cu, Ag and Zn.
 3. A monomeric metal complexaccording to claim 1, wherein M is Cu.
 4. A monomeric metal complexaccording to claim 1, wherein each of R₁ and R₂ is independentlyselected from the group consisting of substituted and unsubstitutedalkyl groups, substituted and unsubstituted alkenyl groups, substitutedand unsubstituted alkynyl groups, substituted and unsubstituted arylgroups, and substituted and unsubstituted heteroaryl groups.
 5. Amonomeric metal complex according to claim 4, wherein R₁ and R₂ are bothisopropyl groups.
 6. A monomeric metal complex according to claim 4,wherein R₁ and R₂ are both phenyl groups.
 7. A monomeric metal complexaccording to claim 1, wherein each of R₃ through R₁₁ is independentlyselected from the group consisting of hydrogen, halogens, hydroxylgroups, cyano groups, alkoxy groups, acyl groups, substituted andunsubstituted alkyl groups, substituted and unsubstituted alkenylgroups, substituted and unsubstituted alkynyl groups, substituted andunsubstituted aryl groups, and substituted and unsubstituted heteroarylgroups.
 8. A monomeric metal complex according to claim 7, wherein atleast one of R₃ through R₁₁ is not hydrogen.
 9. A monomeric metalcomplex according to claim 7, wherein at least R₅ is not hydrogen.
 10. Amonomeric metal complex according to claim 1, wherein one of R₃ throughR₆ and one of R₇ through R₁₁ form a single bond.
 11. A monomeric metalcomplex according to claim 10, wherein R₆ and R₇ form the single bond toform a compound represented by Formula 3:


12. A monomeric metal complex according to claim 1, wherein each of L₁and L₂ is selected from the group consisting of P(CH₃)₃ and P(C₆H₅)₃.13. A monomeric metal complex according to claim 1, wherein L₁ and L₂comprise a single amidophospine ligand to form a compound represented byFormula 6A:


14. A monomeric metal complex according to claim 1, wherein L₁ and L₂comprise a single 1,2-(diisopropylphosphino)ethane ligand to form acompound represented by Formula 6B:


15. A monomeric metal complex comprising a compound represented byFormula 1:

wherein: M is selected from the group consisting of Cu, Ag and Zn; eachof R₁ and R₂ is selected from the group consisting of substituted andunsubstituted alkyl groups, substituted and unsubstituted alkenylgroups, substituted and unsubstituted alkynyl groups, substituted andunsubstituted aryl groups, and substituted and unsubstituted heteroarylgroups; each of R₃ through R₁₁ is selected from the group consisting ofhydrogen, halogens, hydroxyl groups, cyano groups, alkoxy groups, acylgroups, substituted and unsubstituted alkyl groups, substituted andunsubstituted alkenyl groups, substituted and unsubstituted alkynylgroups, substituted and unsubstituted aryl groups, and substituted andunsubstituted heteroaryl groups; and each of L₁ and L₂ is independentlyselected from the group consisting of substituents represented by PX₃,wherein X is selected from the group consisting of alkyl groups, alkenylgroups, alkynyl groups, aryl groups and heteroaryl groups.
 16. Amonomeric metal complex according to claim 15, wherein at least R₅ isnot hydrogen.
 17. A monomeric metal complex according to claim 15,wherein R₆ and R₇ form a single bond to form a compound represented byFormula 3:


18. A monomeric metal complex according to claim 15, wherein L₁ and L₂comprise a single amidophosphine ligand to form a compound representedby Formula 6A:


19. A monomeric metal complex according to claim 15, wherein L₁ and L₂comprise a single 1,2-(diisopropylphosphino)ethane ligand to form acompound represented by Formula 6B:


20. A monomeric metal complex according to claim 14, wherein M is Cu.